Rim rolling machine and method



NOV. 28, 1967 MHDGLEY ET AL 3,355,536

RIM ROLLING MACHINE AND METHOD 2 Sheets-Sheet 1 Filed Aug. 18, 1965INVENTORS Y E I & DM 1, WJ LR CIL R mm VI] ATTORNEYS Nov. 28, 1967 EWDGLEY ET AL 3,355,536

RIM ROLLING MACHINE AND METHOD Filed Aug. 18, 1965 2 Sheets-Sheet 2 FIGSINVENTORS ERIC L. M l DGLEY,

ATTORN EYS United States Patent 3,355,536 REM ROLLING MACHINE AND METHODEric L. Midgley and Carl R. Jank, Danvers, Mass, as-

signors to Sweetheart Plastics, Inc., Wilmington, Mass., a corporationof Maryland Filed Aug. 18, 1965, 501'. No. 480,551 11 Claims. (Cl.264-322) ABSTRACT OF THE DISCLOSURE Rim rolling plastic containerscomprising feeding the containers in nested relationship horizontallyand rotating them in a chamber wherein radiant heaters apply heat to therims evenly While the side wall of each container is protected by sidewall of the next stacked container. Thereafter, the heated rims areturned by the rotating screw rim rollers and are then discharged in ahorizontal direction.

This invention relates to a method and apparatus for rolling the rims ofplastic containers. More particularly, the invention relates to a methodand apparatus for rolling the rims of plastic dishes and cups.

It has long been the practice to form paper cups with rolled rims togive them a finished appearance and added strength, and make them morecomfortable when placed in the month while in use. The same advantagesare derived by rolling the rims of plastic cups and they, too, are nowformed with rolled rims albeit with some difiiculty. Some of thecharacteristics of plastic which make it difficult to roll containerrims are the relative stiffness and brittleness of the material and thenarrow temperature range within which the material may be worked.Further, when the temperature of the stock is in the working temperaturerange, it has very little stiffness and has a tendency to sag anddistort unless supported. Consequently, during the formation of therolled rims it is undesirable to heat the main body of the containerswhich are not subjected to the rolling operation, as they may sag orotherwise distort.

One important object of this invention is to provide apparatus forrolling the rims of containers, which is relatively inexpensive tomanufacture, and which operates at great speed so as to add negligiblyto the cost of the manufacture of the containers.

Another important object of this invention is to provide apparatus forconsistently producing plastic cups or other containers with well-formedrolled rims suitable for further mechanical handling during counting,packaging and vending.

Still another important object of this invention is to provide a methodfor rolling the rims of containers which provides an even curl in therim about the entire periphery of the container.

Yet another important object of this invention is to provide a method ofrolling the rims of containers, which avoids the necessity of contactheating the rims of the containers while confining the heat generally tothe rims being rolled.

To accomplish these and other objects this invention includes among itsfeatures a chamber having means within it for supporting containers innested relationship with the axis of the stack of nested containers in ahorizontal plane. Means are provided adjacent the support for rotatingthe containers while in the nested condition as they move in an axialdirection through the chamber. Radiant heaters are disposed in thechamber for evenly heating the rims of the containers as they movethrough and rotate in the chamber. A plurality of screw rim rollers aredisposed in the chamber, and the threads of the rollers receive the rimsand turn them inwardly as the individual rim rollers are rotated.

These and other objects and features of this invention along with itsincident advantages will be better understood and appreciated from thefollowing detailed description of one embodiment thereof, selected forpurposes of illustration and shown in the accompanying drawing, inwhich:

FIG. 1 is a front view partly in section of a rim rolling machineconstructed in accordance with this invention;

FIG. 2 is a cross-sectional view taken along the corresponding sectionline in FIG. 1;

FIG. 3 is a top View partly in section of the rim rolling machine;

FIGS. 4 and 5 are side views, partly in section, of a cup showing itsrim before and after it has been rolled by the machine; and

FIGS. 6, 7 and 8 are fragmentary cross-sectional views illustrating thesuccessive steps performed by the machine to roll the cup rim.

The machine shown in the drawing includes in its general organization asupporting frame 10 supporting a housing 12 within which the rim rollingoperation takes place, a conveyor mechanism 14 to direct containers intothe housing 12 and a receiving station 16 on which the containers may becounted or otherwise handled after being treated in the chamber 12.Before discussing each of the different components of the machine, thefunction performed by the machine will be described in connection withFIGS. 4 and 5. i

In FIG. 4 a thin-walled plastic cup 20 is shown having a bottom Wall 22,a side wall 24 and a rim 26. The rim 26 includes an upper generallyhorizontal flange 28 and a downturned skirt 30. The rim 26 including thehorizontal flange 28 and the skirt 30 as shown in FIG. 4, are in theconfiguration produced by the cup forming machine and prior to beingsubjected to the rim rolling operation performed by the machine of thisinvention. It will be appreciated that the down-turned skirt 30 if leftin the configuration shown in FIG. 4 would not be comfortable to themonth, particularly because of the exposed downturned edge 32. It willalso be appreciated that the skirt 30 in cooperation with the flange 28and the outer surface of the upper portion of the side wall 24 definesan inverted trough which may collect air or other impurities that wouldmake the cups unusable. Further, the downturned skirt 30 may interferewith or engage the next lower cup in a stack of identical cups nestedtogether in a manner which would interfere with the feeding of such cupsin a vending machine.

The cup shown in FIG. 4 is made acceptable by rolling the rim 26 intothe configuration shown in FIG. 5. In that figure it will be noted thatthe skirt 30 is curled under the horizontal flange 28 to substantiallyclose the troughshaped cavity defined by the skirt and side wall, tohide or confine the raw edge 32 of the skirt so that the rim iscomfortable to the mouth, and to shorten the axial height of the skirtso that it will not interfere with the next lower cup in a nested stack.The machine of this invention imparts to the rim 26 the configurationshown in FIG. 5.

The conveyor mechanism 14 disposed on the right side of the machine asviewed in FIG. 1, includes a conveyor belt 34 supported on an idlerroller 36 and a driven roller 38, and the belt travels in the directionof the arrows 46. A motor 42 on shelf 44 secured to the legs 46 of theframe It) drives the driven roller 38 of the conveyor through a gear box48 and belt and pulley assembly 59.

The upper run 52 of the belt 34 serves as a support for the cups as theyare fed by the conveyor assembly to the treating chamber 12. The cupsare guided along their course on the upper run of the belt by a pair ofrails 53 and 54 that extend from adjacent the idler roller 36 over thetop run 52 of the conveyor and through the housing 12 to the receivingstation 16. In FIGS. 1 and 3 a nested stack of cups is suggesteddisposed on the upper run 52 of the belt 34, the cups being orientedwith their rims 26 facing in the direction of the housing or chamber 12.The cups are fed while stacked in closely nested association by theconveyor belt 34 to a position adjacent opening 56 in the side wall 58of the housing 12.

Disposed above the conveyor mechanism 14 adjacent the driven pulley 38is a rotating brush-like driving wheel 60 also driven by motor 42through gear box 48 and a belt 62. The wheel 60 assists the conveyorbelt 34 in pushing the continuous stack of nested cups, rim first,through the opening 56 in the side wall 58 of the chamber 12. Thedriving wheel 6!] has soft bristles 64 which engage the rims 26 of thecups supported on the upper run 52 of the belt and the rails 53 and 54and rotates clockwise as viewed in FIG. 1.

The housing 12 is defined in part by the side wall 58 and also includesopposite side wall 64 and bottom wall 66, as well as front, back and topwalls (not shown). The walls may be lined with heat insulating material.The rails 53 and 54 extend across the center of the chamber 12 and leavethe chamber through an opening 68 in the side wall 64. As shown in FIG.2, three radiant heaters 70, 72 and 74 extend parallel to the rails 53and 54 within the chamber 12 and are arranged 120 apart with the heater70 directing its heat downwardly above the stack of cups and the heaters72 and 74 disposed slightly below the axis of the cups and direct theirheat to the lower opposite sides.

Disposed below the rails 53 and 54 and positioned to engage the rim 26of each of the cups in the stack is a roller 76 having a knurled surface78 which imparts a rotary motion to the cups as they are pushed throughthe chamber 12 on the rails. The roller 76 as shown in FIG. 1 is drivenby the motor 42 through gear box 48 and a belt 80. The belt 80 engages apulley 82 connected to the end of shaft 84 which supports the roller 76.

The shaft 84 also supports one of three screw-type rim rollers 86. Theothers are identified by reference characters 88 and 90. The screw rimroller 86 carried on shaft 84 rotates at the same speed as the roller76, and the diameter of the roller 76 is substantially the same as thediameter of the screw rim rollers measured across the rim rollergrooves. The screw rim rollers 88 and 90 are geared to the screw rimroller 86 by planetary gears (not shown) or some similar connection, sothat all three screw rim rollers rotate at the same speed and in thesame direction so as to impart the same movement to the rims of thecups. If the shaft 84 is rotating in the direction suggested by arrow92, the screw rim roller 86 rotates clockwise as viewed in FIG. 2, andthe other two screw rim rollers rotate in the same direction.

In the manner shown in FIGS. 6-8, the screw rim rollers 86, 88 and 90turn the down-turned skirts 30 of the rims 26 inwardly to form the rimsinto the configuration shown in FIG. 5.

In FIG. 6 the rim 26 of the cup is shown in engagement with thebeginning of the first volute of the screw rim roller 86. It will benoted that the horizontal flange 28 of the rim bears against the side ofthe volute, and the down-turned skirt of the rim bears against thebevelled portion 93. In FIG. 7 the cup 20 is shown after the screw rimroller 86 has turned through perhaps 180. In that figure the down-turnedskirt is partially turned inwardly by the trailing side 95 of the volute97. In FIG. 8 this skirt is shown fully rolled having traveledapproximately an additional 180" in the volute as the rim roller hasrotated to complete its first revolution. In FIG. 8 it will also benoted that the next container is entering the volute at the inlet point.Thus, in approximately one revolution of the screw rim rollers therolled rim is substantially fully formed, and as the rim continuestotravel through the volute to the rear end of the screw rim rollers, therim has an opportunity to set.

The bevel 93 provided in each of the screw rim rollers first serves toreturn the skirt to its initial position wherein it is substantiallycylindrical with respect to the cup axis if it has moved from thatcondition. The heat applied to the rims as the cups move in the chamber12 has a tendency to cause the rims to uncurl and the skirts 30 to moveradially outward because of the memory of the material. Thus, the bevel93 first corrects the shape of the down-turned skirt and then providesan access for the skirts entering the volutes 97.

After the rims are rolled to the configuration shown in FIG. 5 the cupscontinue to move in nested relationship on the rails 53 and 54 throughthe opening 68 to the receiving station 16. At the station 16 a counteror other device may be used to separate the containers in stacks of anyparticular number, and an operator may remove the counted stacks ofcontainers from the rails and place them in a box or other shippingcarton.

With the foregoing description of the components of the machine, thereader may appreciate some of its advantages and refinements. First, itwill be noted that while the entire body of each cup passes through thechamber 12 containing the radiant heaters 70, 72 and 74, substantiallyonly the down-turned skirts 30 are subjected to the heat of the heatersbecause the cups are in closely nested relationship, and the side walland bottom wall of each cup is contained within the next cup in thestack. Consequently, each cup is protected by the next succeeding cup,and substantially only the skirts 30 of the rims are exposed.

Second, the roller 76 with the knurled surface 78 imparts a uniformrotation to the cups by engaging each of their rims. The roller 76 isrotating at a very substantial speed of perhaps 1,000 r.p.m. so as toimpart a significant speed of rotation to the cups themselves.Consequently, a very uniform application of heat is made to the rims asno portion on the rim perimeter is exposed for a longer period than anyother portion to the heaters 70, 72 and 74. a

The positive action of turning the cups while they are exposed to theradiant heaters insures maximum uniformity of heat distribution.Further, the horizontal orientation of the cups as they pass through thechamber 12 allows each to be supported on the roller 76 so that one cupdoes not interfere with anothers rotation. That is, there is a minimumof frictional contact between adjacent cups so that one does notinterfere with the next and create a jerky or uneven rotation of thecups. Stated in another way, because the containers are on their sides,they will have less of a tendency to key together and adhere to oneanother.

From the foregoing description those skilled in the art will appreciatethe numerous features of this invention. Of particular importance is theability of the machine to apply heat evenly to the rims and of thevolutes' 97 of the screw rim rollers to form an even curl about each ofthe cups. Further, the nested relationship of the cups provides an airinsulation about each cup within the next cup in the row. Consequently,while heat is applied to the rims, a lesser quantity of heat is appliedto the side and bottom walls of the cups, and therefore they are notheated to a forming temperature and do not distort when the rims areheated.

Those skilled in the art will appreciate that numerous modifications maybe made of this invention without departing from its spirit. Moreover,although in the foregoing description the machine is described primarilyin terms of rolling cup rims, it is to be understood that the machinehas wider application. Therefore, it is not intended that the breadth ofthis invention be limited to the single embodiment illustrated anddescribed. Rather it is intended that the scope of this invention bedetermined by the appended claims and their equivalents.

What is claimed is:

1. A machine for rolling the rims of thin-walled plastic nestable cupshaving side and bottom walls and a rim comp-rising

9. A METHOD OF FORMING ROLLED RIMS ON CONTAINERS HAVING RIMS WITH SKIRTSCOMPRISING THE STEPS OF FEEDING THE CONTAINERS IN NESTED RELATIONSHIPHORIZONTALLY THROUGH A HEATING CHAMBER TO RAISE THE TEMPERATURE OF THESKIRTS WITHIN THE FORMABLE RANGE, IMPARTING ROTATION DIRECTLY TO EACHCONTAINER TO APPLY AN EVEN APPLICATION OF EHAT TO THE RIMS WHILE THECONTAINERS ARE IN THE NESTED RELATIONSHIP, AND THEREAFTER PASSING THERIMS THROUGH THE VOLUTES OF A NUMBER OF THREDED ROLLERS TO BEND THESKIRTS INWARDLY TOWARD THE CONTAINER AXIS.